EP0152433A1 - Method of producing a filtered beam of light. - Google Patents

Method of producing a filtered beam of light.

Info

Publication number
EP0152433A1
EP0152433A1 EP84903027A EP84903027A EP0152433A1 EP 0152433 A1 EP0152433 A1 EP 0152433A1 EP 84903027 A EP84903027 A EP 84903027A EP 84903027 A EP84903027 A EP 84903027A EP 0152433 A1 EP0152433 A1 EP 0152433A1
Authority
EP
European Patent Office
Prior art keywords
light
source
filter
film
photographic film
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP84903027A
Other languages
German (de)
French (fr)
Other versions
EP0152433B1 (en
Inventor
Ronald A Ferrante
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
NCR Voyix Corp
Original Assignee
NCR Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by NCR Corp filed Critical NCR Corp
Publication of EP0152433A1 publication Critical patent/EP0152433A1/en
Application granted granted Critical
Publication of EP0152433B1 publication Critical patent/EP0152433B1/en
Expired legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
    • G02B27/09—Beam shaping, e.g. changing the cross-sectional area, not otherwise provided for
    • G02B27/0927—Systems for changing the beam intensity distribution, e.g. Gaussian to top-hat
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B26/00—Optical devices or arrangements for the control of light using movable or deformable optical elements
    • G02B26/08—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the direction of light
    • G02B26/10—Scanning systems
    • G02B26/106—Scanning systems having diffraction gratings as scanning elements, e.g. holographic scanners
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
    • G02B27/09—Beam shaping, e.g. changing the cross-sectional area, not otherwise provided for
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
    • G02B27/09—Beam shaping, e.g. changing the cross-sectional area, not otherwise provided for
    • G02B27/0938—Using specific optical elements
    • G02B27/0944—Diffractive optical elements, e.g. gratings, holograms
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/20—Filters
    • G02B5/205—Neutral density filters
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/32—Holograms used as optical elements

Definitions

  • the present invention is directed to a method of producing a filtered beam of light.
  • a hologram is the name given to a photographic film having an interference pattern recorded thereon.
  • the interference pattern is usually produced by a source of coherent light which is normally split into two beams, one of which is directed onto the sheet of photographic film, and the other of which is directed onto a subject.
  • the beam directed onto the subject is scattered onto the sheet of film with waves of varied orientation and wave front curvature.
  • the scattered light waves and the undisturbed beam are reunited at the film where they interfere as patterns of light and dark areas which are photographically recorded.
  • a source of coherent light When a source of coherent light is directed through the patterned film sheet, it is diffracted into a number of diffraction orders. At least one of these orders duplicates the waves that were originally reflected from the subject, and a person viewing the film sees the subject of the hologram in three dimensions, with the subject appearing behind the hologram at a distance equal to the original subject to film distance. If the viewer changes his position and views the hologram from a different angle, the three-dimensional perspective changes and the viewer may thus look around an object in the foreground to see an object behind it.
  • Holograms have been utilized in scanning an object such as a UPC coded label to read the data contained therein.
  • An example of such a scanning arrangement may be found in ⁇ . S. Patent
  • a method of producing a filtered beam of light characterized by the steps of providing a source of light having an intensity which varies from point to point over its cross-sectional area; positioning a photographic film in the beam of light at a predetermined distance from said source; exposing the photographic film to the beam of light; developing the exposed photographic film; and reinserting the developed film at said predetermined distance from the source for selectively absorbing portions of the light passing therethrough.
  • FIG. 1 is a schematic representation of a prior art system for constructing a holographic disc used in a holographic scanning system.
  • Fig. 2 is a schematic representation of a 5 system for constructing the Gaussian beam filter of the present invention.
  • Fig. 3 is a diagram of the theoretical power transmission of a number of photographic Gaussian filters using Kodak 649F photographic plates.
  • Fig. 4 is a diagram of the measured power transmission of the filters shown in Fig. 3.
  • Fig. 5 is a diagram of the theoretical power transmission of a number of photographic Gaussian filters using Agfa 8E75HD photographic plates.
  • Fig. 6 is a diagram of a theoretical comparison of the fifth order filter and the Kodak 649F photographic plate.
  • FIG. 1 there is shown a
  • FIG. 20 schematic representation of a prior art system for constructing a holographic disk which is used in a holographic scanning system.
  • the system includes a 50 mW helium-neon laser 20 whose light output is directed toward a mirror 22 which deflects the light
  • the beam segment 26 is directed toward the mirror 30 which deflects the beam segment through a spatial filter 32 which in turn directs the light beam through a pinhole spatial
  • the filter 34 for focusing on the mask 36 of the disc 38.
  • the light beam segment 28 is directed to a mirror 40 which deflects the light beam segment through a spatial filter 42 which in turn directs the light beam segment through a pinhole spatial filter 44 toward a 5 collimating lens 46 for directing the collimated light beam on the mask 36.
  • The.light beam segment 26, when focused on the mask 36, will function as the object beam, while the collimated light beam segment 28 transmitted through the lens 46 will function as a reference beam, thereby generating the interference fringes on the mask 36 which are exposed in a layer of dichromated gelatin located on the disc 38.
  • a photographic plate 50 such as Kodak 649F was inserted in front of a helium-neon laser 52 at a distance d exposing the plate to the light output of the laser.
  • the exposed plate 50 was then developed for five minutes in Developer D-19, treating the plate for one minute in the Stop Bath SB- 1, fixing the plate for ten minutes in a rapid fixer solution, washing the fixed plate in water for ten minutes, washing the plate for five minutes in a 50/50 solution of water and Isopropanol, washing the plate for five minutes in a 100% solution of Isopropanol and air drying the plate.
  • a cover plate is ce eted over the plate for environmental protection.
  • the developed plate 50 was reinserted at its original position where it was found that the plate attenuated most strongly the central portion of the laser's output beam thus eliminating the original Gaussian irradiance profile of the laser beam. Where that portion of the laser beam has the highest light intensity, the corresponding portion of the developed photographic plate is the darkest limiting the amount of the light passing through the plate. . Those . portions of the laser having the lowest light
  • the corresponding portion of the plate will be the lightest.
  • the filtered output of the plate is directed through a microscopic object lens 54 and spatially filtered by pinhole filter 56 which produces a noise free, constant irradiance coherent laser beam projected on an output plane where the amount of light is detected and measured by an optical detector 58 such as the UDT Model 181 Radiometer.
  • an optical detector 58 such as the UDT Model 181 Radiometer.
  • FIG. 3 and 4 disclose the irradiance profile of the power transmission of a laser without a filter showing the pronounced Gaussian effect.
  • Curve 62 shown in Fig. 4 shows the output of a filter exposed to the output of a laser for 0.10 seconds; curve 64 is exposed for 0.106 seconds; curve 66 exposed 0.119 seconds and curve 68 exposed for 0.163 seconds. It will be seen from Fig. 4 that as the time of exposure of the filter to the laser output increases, a flattening of the sharply peaked Gaussian input beam transmitted through the photographic filter occurs.
  • Fig. 5 shows the theoretical irradiance profile of a number of filters recorded on Agfa 8E75HD photographic plates while Fig.
  • FIG. 6 is a theoretical comparison of a fifth order filter and the Kodak 649K photographic filter. It will be seen in comparing the curve of Fig. 5 with those of Fig. 3 that the response of both emulsions are very similar in which both Figures predict a flattening of the- Gaussian input beam. At higher exposures overmodulation is seen to produce a "hole" in the be center. For comparison.
  • Fig. 6 shows the curve 72 of the fifth order filter to have a slightly broader correction than the curve 74 of the 649F filter with a somewhat more rapid edge fall-off, both desirable filter characteristics. It is obvious that the photographic absorption filter constructed in accordance with the invention is very inexpensive compared to the manufactured metallic thin film filters.

Landscapes

  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Holo Graphy (AREA)
  • Optical Head (AREA)
  • Non-Silver Salt Photosensitive Materials And Non-Silver Salt Photography (AREA)

Abstract

Dans un procédé de production d'un faisceau de lumière cohérente d'intensité uniforme, un film photographique (50), positionné à une distance prédéterminée (d) d'une source lumineuse (52), est exposé à un faisceau de lumière cohérente d'intensité non uniforme et variant d'un point à l'autre sur sa section transversale suivant une fonction de Gauss prédéterminée, émis par cette source (52). Le film est ensuite développé et réinséré à ladite distance prédéterminée (d) de la source lumineuse (52) pour servir de filtre absorbant sélectivement des parties de la lumière le traversant. Ce faisceau lumineux d'intensité uniforme est utilisé avantageusement pour produire les hologrammes utilisés dans les appareils de balayage d'hologrammes.In a method of producing a beam of coherent light of uniform intensity, a photographic film (50), positioned at a predetermined distance (d) from a light source (52), is exposed to a beam of coherent light d non-uniform intensity varying from one point to another on its cross-section according to a predetermined Gaussian function, emitted by this source (52). The film is then developed and reinserted at said predetermined distance (d) from the light source (52) to serve as a filter selectively absorbing portions of the light passing through it. This light beam of uniform intensity is advantageously used to produce the holograms used in hologram scanners.

Description

METHOD OF PRODUCING A FILTERED BEAM OF LIGHT
Technical Field
The present invention is directed to a method of producing a filtered beam of light.
Background Art
A hologram is the name given to a photographic film having an interference pattern recorded thereon. The interference pattern is usually produced by a source of coherent light which is normally split into two beams, one of which is directed onto the sheet of photographic film, and the other of which is directed onto a subject. The beam directed onto the subject is scattered onto the sheet of film with waves of varied orientation and wave front curvature. The scattered light waves and the undisturbed beam are reunited at the film where they interfere as patterns of light and dark areas which are photographically recorded.
When a source of coherent light is directed through the patterned film sheet, it is diffracted into a number of diffraction orders. At least one of these orders duplicates the waves that were originally reflected from the subject, and a person viewing the film sees the subject of the hologram in three dimensions, with the subject appearing behind the hologram at a distance equal to the original subject to film distance. If the viewer changes his position and views the hologram from a different angle, the three-dimensional perspective changes and the viewer may thus look around an object in the foreground to see an object behind it.
Holograms have been utilized in scanning an object such as a UPC coded label to read the data contained therein. An example of such a scanning arrangement may be found in ϋ. S. Patent
OMH No. 4,224,509. In manufacturing the holograms used in the above cited scanning apparatus, a laser is used as a source of coherent light. Where it is required that coherent light be of uniform illumination, objective lenses are used to expand the beam and then limit the expansion with a collimating lens since the laser projects a beam whose cross-sectional profile is approximately Gaussian. In order to overcome this deficiency in a laser beam, optical filters have been proposed. An example of such a filter may be found in the ϋ. S. Patent No. 3,465,347 which consists essentially of a glass substrate with a spherical surface having a layer of light absorbing material. The cost of such a filter is quite expensive.
Disclosure of the Invention
It is, therefore, the object of this invention to provide a low cost optical filter which will produce a beam from a light source, which beam has uniform intensity. Thus, according to the invention, there is provided a method of producing a filtered beam of light characterized by the steps of providing a source of light having an intensity which varies from point to point over its cross-sectional area; positioning a photographic film in the beam of light at a predetermined distance from said source; exposing the photographic film to the beam of light; developing the exposed photographic film; and reinserting the developed film at said predetermined distance from the source for selectively absorbing portions of the light passing therethrough.
Brief Description of the Drawings
Embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, wherein like numerals identify corresponding elements. Fig. 1 is a schematic representation of a prior art system for constructing a holographic disc used in a holographic scanning system.
Fig. 2 is a schematic representation of a 5 system for constructing the Gaussian beam filter of the present invention.
Fig. 3 is a diagram of the theoretical power transmission of a number of photographic Gaussian filters using Kodak 649F photographic plates.
•* 10 Fig. 4 is a diagram of the measured power transmission of the filters shown in Fig. 3.
Fig. 5 is a diagram of the theoretical power transmission of a number of photographic Gaussian filters using Agfa 8E75HD photographic plates. 15 Fig. 6 is a diagram of a theoretical comparison of the fifth order filter and the Kodak 649F photographic plate.
Best Mode for Carrying Out the Invention
Referring now to Fig. 1, there is shown a
20 schematic representation of a prior art system for constructing a holographic disk which is used in a holographic scanning system. The system includes a 50 mW helium-neon laser 20 whose light output is directed toward a mirror 22 which deflects the light
25 beam into a beam splitter 24 splitting the beam into two light beam segments 26 and 28. The beam segment 26 is directed toward the mirror 30 which deflects the beam segment through a spatial filter 32 which in turn directs the light beam through a pinhole spatial
30 filter 34 for focusing on the mask 36 of the disc 38. The light beam segment 28 is directed to a mirror 40 which deflects the light beam segment through a spatial filter 42 which in turn directs the light beam segment through a pinhole spatial filter 44 toward a 5 collimating lens 46 for directing the collimated light beam on the mask 36. The.light beam segment 26, when focused on the mask 36, will function as the object beam, while the collimated light beam segment 28 transmitted through the lens 46 will function as a reference beam, thereby generating the interference fringes on the mask 36 which are exposed in a layer of dichromated gelatin located on the disc 38.
In order to reduce the cost of manufacturing the holographic disc 38, it was found that by exposing a photographic film to the output of a laser and after developing the film, reinserting the exposed film at its original position, the output beam of the filter was of a uniform illumination. In fabricating such a filter, a photographic plate 50 (Fig. 2) such as Kodak 649F was inserted in front of a helium-neon laser 52 at a distance d exposing the plate to the light output of the laser. The exposed plate 50 was then developed for five minutes in Developer D-19, treating the plate for one minute in the Stop Bath SB- 1, fixing the plate for ten minutes in a rapid fixer solution, washing the fixed plate in water for ten minutes, washing the plate for five minutes in a 50/50 solution of water and Isopropanol, washing the plate for five minutes in a 100% solution of Isopropanol and air drying the plate. After the plate has been dried, a cover plate is ce eted over the plate for environmental protection. After developing, the developed plate 50 was reinserted at its original position where it was found that the plate attenuated most strongly the central portion of the laser's output beam thus eliminating the original Gaussian irradiance profile of the laser beam. Where that portion of the laser beam has the highest light intensity, the corresponding portion of the developed photographic plate is the darkest limiting the amount of the light passing through the plate. . Those . portions of the laser having the lowest light
O PI ∞ intensity, the corresponding portion of the plate will be the lightest. In measuring the light output of the plate 50, the filtered output of the plate is directed through a microscopic object lens 54 and spatially filtered by pinhole filter 56 which produces a noise free, constant irradiance coherent laser beam projected on an output plane where the amount of light is detected and measured by an optical detector 58 such as the UDT Model 181 Radiometer. Referring now to Figs. 3 and 4, there is shown a diagram of the irradiance profile of a number of filters recorded on Kodak 649K on photographic plates and constructed in accordance with the present invention. Fig. 3 shows the theoretical filter transmission while Fig. 4 shows the measured transmission for the same filter. Curve 60 and both Figs. 3 and 4 disclose the irradiance profile of the power transmission of a laser without a filter showing the pronounced Gaussian effect. Curve 62 shown in Fig. 4 shows the output of a filter exposed to the output of a laser for 0.10 seconds; curve 64 is exposed for 0.106 seconds; curve 66 exposed 0.119 seconds and curve 68 exposed for 0.163 seconds. It will be seen from Fig. 4 that as the time of exposure of the filter to the laser output increases, a flattening of the sharply peaked Gaussian input beam transmitted through the photographic filter occurs. In a similar manner Fig. 5 shows the theoretical irradiance profile of a number of filters recorded on Agfa 8E75HD photographic plates while Fig. 6 is a theoretical comparison of a fifth order filter and the Kodak 649K photographic filter. It will be seen in comparing the curve of Fig. 5 with those of Fig. 3 that the response of both emulsions are very similar in which both Figures predict a flattening of the- Gaussian input beam. At higher exposures overmodulation is seen to produce a "hole" in the be center. For comparison. Fig. 6 shows the curve 72 of the fifth order filter to have a slightly broader correction than the curve 74 of the 649F filter with a somewhat more rapid edge fall-off, both desirable filter characteristics. It is obvious that the photographic absorption filter constructed in accordance with the invention is very inexpensive compared to the manufactured metallic thin film filters.

Claims

WHAT IS CLAIMED IS:
1. A method of producing a filtered beam of light characterized by the steps of providing a source of light (52) having an intensity which varies from point to point over its cross-sectional area; positioning a photographic film (50) in the beam of light at a predetermined distance (d) from said source (52) ; exposing the photographic film to the beam of light; developing the exposed photographic film (50) ; and reinserting the developed film (50) at said predetermined distance (d) from the source (52) for selectively absorbing portions of the light passing therethrough.
2. A method according to claim 1, characterized in that said source of light (52) provides a coherent beam of light of nonuniform intensity which varies from point to point over its cross-sectional area in accordance with a predetermined Gaussian function.
3. A method according to claim 1, characterized in that the photographic film (50) is Kodak 649F photographic film exposed for 0.163 seconds to the source of light.
EP84903027A 1983-08-01 1984-07-30 Method of producing a filtered beam of light Expired EP0152433B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US51944183A 1983-08-01 1983-08-01
US519441 1983-08-01

Publications (2)

Publication Number Publication Date
EP0152433A1 true EP0152433A1 (en) 1985-08-28
EP0152433B1 EP0152433B1 (en) 1988-03-02

Family

ID=24068319

Family Applications (1)

Application Number Title Priority Date Filing Date
EP84903027A Expired EP0152433B1 (en) 1983-08-01 1984-07-30 Method of producing a filtered beam of light

Country Status (6)

Country Link
US (1) US4605606A (en)
EP (1) EP0152433B1 (en)
JP (1) JPS60501917A (en)
CA (1) CA1251624A (en)
DE (2) DE3469604D1 (en)
WO (1) WO1985000667A1 (en)

Families Citing this family (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1986004155A1 (en) * 1984-12-28 1986-07-17 Ncr Corporation Method of producing a gaussian laser beam filter
US5340637A (en) * 1986-09-16 1994-08-23 Hitachi, Ltd. Optical device diffraction gratings and a photomask for use in the same
JPS6438890U (en) * 1987-09-02 1989-03-08
US5111343A (en) * 1990-05-29 1992-05-05 Eastman Kodak Company Gradient filter
JPH05238023A (en) * 1992-02-27 1993-09-17 Fuji Photo Film Co Ltd Thermal recorder
EP0580905A1 (en) * 1992-07-28 1994-02-02 BRITISH TELECOMMUNICATIONS public limited company Optical radiation devices
US5331468A (en) * 1992-11-27 1994-07-19 Eastman Kodak Company Intensity redistribution for exposure correction in an overfilled symmetrical laser printer
US6008835A (en) * 1995-10-30 1999-12-28 Ricoh Company, Ltd. Image forming device utilizing laser beam
JPH09288444A (en) * 1996-04-23 1997-11-04 Komatsu Ltd Confocal optical device and hologram exposure device
JP6193305B2 (en) 2014-07-29 2017-09-06 ウルトラテック インク High performance line forming optical system and method
US9613815B2 (en) 2014-11-24 2017-04-04 Ultratech, Inc. High-efficiency line-forming optical systems and methods for defect annealing and dopant activation
CN113534471B (en) * 2020-04-15 2022-06-03 清华大学 Method and device for generating three-dimensional wave packet track coupled light beam outside cavity

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US1953471A (en) * 1932-01-05 1934-04-03 Electrical Res Prod Inc Optical instrument
US3149968A (en) * 1960-12-21 1964-09-22 Lloyd D Stephens Apparatus for correcting sensitivity variations in photomultiplier tubes
US3582326A (en) * 1963-10-18 1971-06-01 Sylvania Electric Prod Photographic process for forming a light intensity correcting filter used in exposing a color crt screen
US3465347A (en) * 1967-10-11 1969-09-02 Rca Corp Laser recorder with optical filter
US3676129A (en) * 1969-12-01 1972-07-11 Rca Corp Method for making a light intensity correction filter
US3700314A (en) * 1971-04-07 1972-10-24 Ampex Variable light transmitting filter for cameras
JPS4980252U (en) * 1972-10-28 1974-07-11
NL7810313A (en) * 1977-11-22 1979-05-25 Elliott Brothers London Ltd METHOD AND ARRANGEMENT FOR REGULATING THE INTENSITY OF LIGHT IN AN OPTICAL SYSTEM.

Non-Patent Citations (1)

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Title
See references of WO8500667A1 *

Also Published As

Publication number Publication date
EP0152433B1 (en) 1988-03-02
CA1251624A (en) 1989-03-28
DE152433T1 (en) 1986-07-24
JPS60501917A (en) 1985-11-07
DE3469604D1 (en) 1988-04-07
WO1985000667A1 (en) 1985-02-14
US4605606A (en) 1986-08-12

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